JavaScript Why do I get the error message "undefined"?

[Joesson]

Hello, newbie here. Why does this code tell me that lastElement is undefined?

function lastElement ([Good, Bad, Ugly])
{
    let index = lastElement.indexOf('Ugly');
    return index;
 
}

lastElement('Loafy', 'Boafy', 'Goafy');

I also tried a different version of it, which returns as undefined as well:

function lastElement ([val1, val2, val3])
{
    let index = lastElement[lastElement.length -1];
    return index;
 
}

lastElement('Loafy', 'Boafy', 'Goafy');

I thought that the contents of 'lastElement' would be defined by the user when passing the argument, and so by then it would be defined? What am I missing?

I am trying to return the last element of the array, when the function is called.

Thanks!

 

[OldMan]

indexOf() give the first occurrence of a value in a string. Try this just to see the difference.
<script>
function lastElement ([Good, Bad, Ugly])
{
let text = "Good, Bad, Ugly";
let index = text.indexOf('Ugly');
return index;

}
let Bill = lastElement('Loafy', 'Boafy', 'Goafy');
alert(Bill);
</script>You are not going to get Goafy . If that is what you want to get Use arguments[2]. Arguments are in an array so theyb start with zero.

 

[Joesson]

Thanks for the explanation, OldMan, now things make more sense to me. : )